Open AccessUsing hyperpolarized 129Xe gas-exchange MRI to model the regional airspace, membrane, and capillary contributions to diffusing capacity
Author(s) -
Z Wang,
Leith Rankine,
E. Bier,
David Mummy,
Junlan Lu,
A. H. Church,
Robert Tighe,
Aparna Swaminathan,
YuhChin T. Huang,
Loretta G. Que,
J. Mammarappallil,
Sudarshan Rajagopal,
Bastiaan Driehuys
Publication year - 2021
Publication title -
journal of applied physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.253
H-Index - 229
eISSN - 8750-7587
pISSN - 1522-1601
DOI - 10.1152/japplphysiol.00702.2020
Subject(s) - diffusing capacity , pulmonary diffusing capacity , chemistry , carbon monoxide , volume (thermodynamics) , capillary action , membrane , nuclear magnetic resonance , lung , medicine , thermodynamics , physics , biochemistry , lung function , catalysis
Hyperpolarized 129 Xe MRI has emerged as a novel means to evaluate pulmonary function via 3D mapping of ventilation, interstitial barrier uptake, and RBC transfer. However, the physiological interpretation of these measurements has yet to be firmly established. Here, we propose a model that uses the three components of 129 Xe gas-exchange MRI to estimate accessible alveolar volume ( V A ), membrane conductance, and capillary blood volume contributions to DL CO . 129 Xe ventilated volume (VV) was related to V A by a scaling factor k V = 1.47 with 95% confidence interval [1.42, 1.52], relative 129 Xe barrier uptake (normalized by the healthy reference value) was used to estimate the membrane-specific conductance coefficient k B = 10.6 [8.6, 13.6] mL/min/mmHg/L, whereas normalized RBC transfer was used to calculate the capillary blood volume-specific conductance coefficient k R = 13.6 [11.4, 16.7] mL/min/mmHg/L. In this way, the barrier and RBC transfer per unit volume determined the transfer coefficient K CO , which was then multiplied by image-estimated V A to obtain DL CO . The model was built on a cohort of 41 healthy subjects and 101 patients with pulmonary disorders. The resulting 129 Xe-derived DL CO correlated strongly ( R 2 = 0.75, P < 0.001) with the measured values, a finding that was preserved within each individual disease cohort. The ability to use 129 Xe MRI measures of ventilation, barrier uptake, and RBC transfer to estimate each of the underlying constituents of DL CO clarifies the interpretation of these images while enabling their use to monitor these aspects of gas exchange independently and regionally. NEW & NOTEWORTHY The diffusing capacity for carbon monoxide (DL CO ) is perhaps one of the most comprehensive physiological measures used in pulmonary medicine. Here, we spatially resolve and estimate its key components-accessible alveolar volume, membrane, and capillary blood volume conductances-using hyperpolarized 129 Xe MRI of ventilation, interstitial barrier uptake, and red blood cell transfer. This image-derived DL CO correlates strongly with measured values in 142 subjects with a broad range of pulmonary disorders.